Anisotropy in Thermal Transport Properties of Cast γ-TiAl Alloys

Artikel i vetenskaplig tidskrift, 2001

The thermal transport properties have been determined for titanium aluminide with nominal composition Ti-48Al-2W-0.5Si (at.%), cast to cylindrical bars with different gamma/(gamma + alpha(2)) microstructures. The amount of phases and the orientation of the lamellar plates vary from the core to the rim in each of the bars. Differences in the thermal conductivity of the two phases lead to anisotropy in the thermal transport properties, but with cylindrical symmetry in the bars. A newly developed, high-precision technique, the so-called transient plane source (TPS) technique, was used to resolve the anisotropy in a wide temperature range. Typically, the conductivity increases monotonously from about 12- 14 W/m center dot K at room temperature up to about 20-22 W/m center dot K at 700 degrees C for the different materials. The anisotropy in both conductivity and diffusivity is about 15% at all temperatures, but with fundamental differences between the different materials. The anisotropy of the transport properties is explained in terms of amounts of phases and directionality of the lamellar plates.